Automatic telephone system



Feb. 18, 1930. 1,747,402

AUTOMATIC TELEPHONE SY STEM Filed Feb. 20, 1928 mran ui" UIETITJ? E'Tharp Patented Feb. 18, 1930 UNITED srarssl smear car es VICTOR s. THARP, or ELMHUBST, rumors, Assrenoit' 'ro nnsnnvn HOLDING COM- IPANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF DELAWARE AUTOMATIC TELEPHONE SYSTEM Application filed February 20, 1928. Serial No. 255,537.

The present inventionrelates to automatic telephone systems in general, but is concerned more particularly with multi-office automatic telephone systems in which there are two tlifierent kinds of oflices or exchanges, and.

Strowger type of system, that is, the

two systems have automatic switches which are operated on the wellknown Strowger step-by-step principle. The switches of the two systems are therefore somewhat similar in mechanical construction but differ considerable in regard to switch control and supervision. The standard method of switch control in one type of system (the one used in the UnitedStates) is over a two wire metallic loop and supervision is controlled by the reversal of battery over the two talking leads. This type of system will, be re- ,25 ferred to hereinafter as a two-wire loop' system. In the other type of system, switch control is over only one of the talking conductors, commonly referred to as the A or negative talking conductor, and supervision is controlled over the other talking conductor, commonly referred to as B or'positive talking conductor. This latter type of system is manufactured by the Mix and Genest Telephone and Telegraph. Company of Berlin, Germany, .and will bereferrcd to hereinafter as the battery pulse system or the Mix and Genest system.

The two systems are also different in regard to the method of, giving the calling subscriber a busy tone when a busy line is encountered. In the two wire loop system when the connector or last switch in the train encounters a busy line, the busy relay in the connector energizes and connects up the busy 7 machine, thereby giving the calling subscriber the busy tone. The operated switches are maintained in operated position until the calling party hangs up his receiver. In the battery pulse system when the last switch inthe train encounters a busy line, all but the first of the switches automatically release responsive thereto and the busy tone is transmitted to the calling subscriber from the first switch in the switch train.

In order to provide telephone service between subscribers in the two different types of systems, as above described, a group of; 1

two-way trunk'lines extends from an office of the two wire type and terminates in incoming andoutgoing repeaters in an office of the so called battery pulse type,

One of the features of the present invention relates to an incoming repeater which translates the two wire loop impulses received over the two incoming trunk conductors and transmits a corresponding number of interrupted negative battery impulses over the outgoing negative talking conductor or A lead; which trans lates the grounded switch supervision received over the outgoing positive talking conductor or B lead and transmits reverse battery over the two incoming talking conductors; and which connects the busytone to the incoming trunk when the last switch of the train encounters a busy condition and all ofthe operated switches in the battery pulse ofiice included in the connection release responsive to the encountered busy condition.

Another-feature of the invention relates to an outgoing repeater which translates the negative battery impulses received over the incoming negative lead and transmits a cor responding number of two-wire loop im pulses over the two outgoing talking conductors of the trunk, and which translates the reverse battery supervision, which is received over the two outgoing talking conductors of the trunk, to supervision over only the posh tive incoming talking conductor, or the B lead, by connecting ground to such conductor responsive to receiving the reverse batterv supervision. These and other features of the invention not specifically mentioned at this time will be better appreciated when the following description is taken in conjunction with the accompanying drawings.

Referring now to drawings, there is shown by means of the usual circuit diagram, the

7 new and improved outgoing and incoming repeaters OR and IR, respectively, located in one-of. the ofiices in the so calledbattery pulse system, one of the trunks comprising the conductors land 2 extending to a distant ofiice of the so called two wire loop system,

and the selector switches S and 1S located in the battery pulse office.

The outgoing repeaters, such as OR,- comprise a plurality ofrelaysfand are taken into use'by calling'subscribers, having lines'termi- L natingin the "battery pulse othce, for extend 1 3 1 ductors land 2. V are accessible to the calling. subscribersrby ing connections to called subscribers located --in the distant two-wire loopoifices .oyertrunks'such as the trunk comprising con- The outgoing repeaters-OR way of se'lector'ssu'ch as S. v

r The incoming repeaters, such as 'comprise a plurality of relays and are taken into -use by thedistant calling subscribers in the l two wire 100p ofilce over trunks such as the trunk comprising conductors 1 and 2 for eit tending connections to called subscribers by way of the incoming selectors, su'chyasbse lector IS, in the battery pulse ofiice. The incoming first selectorsw'itches, such 3 as IS,;are located in, the battery pulse fiice the banks of theregular first selectors in the;

and are vertical and rotary step-bystep' switches similar in mechanical-construction to the well known two-wire Strowger type of switch. The switch control circuits of which, however, are different from the Stro-wger' switches of the wellknown; two-wire loop type'as previously described. The banks of the selector-s IS are'connected' in multiple to I battery pulse office. a s v'The selectors, such as S, are also located in the battery pulse ofliceand are somewhat similar to the selectors IS, 1 The selectors S have access to; repeaters, suchas OR, and may be either, first, second, third or fourth selectors dependent upon the trunking layout in thebattery pulse office. a y

, The remaining switches and trunking *arrangementsin the two systems being Well i understood"and formingno part of thepresent invention, are therefo shown in the drawings.

'With this general description of the draw ing in mind, the operation of the repeater circuits will now be explained in detail. For

' thisfpurpose, it will be assumed that a call '55 ing subscriber in the distant two-wire .loop

7 office desires to obtain a connectionwith a called subscriber whose line terminates in -the seized selector repeater seizes an'idle re not described or trunk extending to the desired oflice. Let us, a

now assume that the trunk comprising the conductors 1 and '2 is the trunk seized by the line switch. Responsive to the seizure of this trunk, a closed loop circuit for energizing the line relay 31 of the incoming rep'eater IR may be traced overthetrunk conductors 1 and 2, armatures 10 and 12 and theirf'resting contacts, normallyclosed springs com 7 trolled by armatures 38 and 39, and upper and lower windings of line relay'31 to bat tery and .groi'ind, respectively. 7 7

Line relay 31 energizes over the above traced circuit and at armature 4O prepares 80 a circuit for repeating negative battery impulses overthe a or negative conductor to the line relay in the incoming selector IS. 'At i armature '41 relay 31y=closes an energizing V circuit for'the slow to release relay 32. Re

lay 32, upon energizing,at armature 42 closes a circuit over the a conductor-tothe line relay in the selector T8 for preparingsuc h switch for operation; at armature 43 pre -i pares a lock-ing circuit for relay 33; at arma ture 44 closes a circuit for energizing relay the selector IS; and at armature 45 prepares 7 34 and for re arin 'a'holdin circuit-for f a circuit for energizing slow to release relay 35. The circuit for energizing relay 34mayJ may be traced as follows; groundedarmature 44, armature '47, winding of relay 34,

the Ulead or heldi-ngconductor, tobattery in the incoming selector IS. Relay 34, f

upon energizing, at armature 49 closes .a circult for relay 33'; at armature 50closes' a loc king circuit for'itself; and at armature 51 dis= connects thebusy tone machine. -Relaya33, Q

upon: energizing, at armature 5'4 removes-the battery potential from conductors and 2-7,

thereby rendering the outgoing repeaterfOR busyto selectors, such as S,--having'access 7 fly thereto at armature 46 closes a'locking 'cire cuit for itself; at armature 47-opens the initial energizing circuit of relay 34; and at armature 48 prepares a circuit for connecting the busy tone to the lower talking conductor.

Responsiveto the seizure of the incoming selector IS, as above described,the line relay in-such selector energizes and-closes a circuit over the C leador holding conductor for anotherrelay in the incoming selector IS which prepares the selector for its vertical operation. I

The calling subscriber'may'now dial the re mainingdi-gits in the telephone number '03": the called subscriber. When the calling fsubscriber operateshis calling device in accord ance with the next digit in the telephone number of the called subscriber, the circuit of the line relay 31 is interrupted aplurali'ty of times thereby causing said relayto release a like number of times. Upon thefirstdeenerg'ization 01: line relay $31 a circuit is closed from armature 41 and its rest-ingaconta'ct for energizing the-slowtoreleaserelay35. Relay energizes and at armatures 52 and 53 opens the circuits to the talking condensers of the repeater IR. At armature 40, relay 31 interrupts or opens the switch control or impulsing circuit to the incoming first selector IS thereby causing the line relay in the selector TS to deenergize. For each interruption in the loop circuit extending over the conductors 1 and 2 the line'relay 31 at armature 4O interrupts the circuit of the line relay in the incoming selector IS, thereby causing said switch to operate in the well known manner. It well be mentioned at this time that the slow to release relay 32 is maintained energized throughout the impulsing period and that relay 35 due to its slow to release characteristics maintains its armatures attracted during each series of impulses. The interrupted negative battery impulses transmitted over the a conductor to the incoming selector ISand to subsequent selectors in the battery pulse oilice cause said switches to extend the connection in a well known manner to the line of the desired called subscriber. I

Assuming now that the called line is bus the operated switches in the battery pulse ofiice automatically releases responsive to the connector or last switch in the train encountering a busy line. In the incoming selector- IS, the release magnet removes battery from the C lead thereby opening the circuit of:

- relay 34 which deenergizes. Relay 34, upon deenergizing, at armature 51 connects the busy tone machine to the lower talking conductor thereby transmitting the busy tone to thecalling subscriber in the well known manner. The calling subscriber upon hearing the busy signal replaces his receiver and the release of the connection takes place in amanher to be described hereinafter.

We will now assume that the called line is idle. Under these conditions, the called subscribers bell is rung in the usual manner. When the called party answers responsive thereto a relay in the last switch in the train connects ground tothe lower talking conductor of such switch. This same ground extends over the intermediate switches to the For lower talking conductor of the repeater, thereby causing the energization of the reversing relay 30. Relay 30, upon energizing, at armatures 38 and 39 reverses the direction of current flow over the conductors'l and 2 for operatin g the calling subscribers meter or for 1 other supervisory purposes. At armature 37 relay 30 includes the high resistance winding of impedance 36 in the impulse circuit over the a lead.

When conversation is finished both subscribers hang up their receivers and the operated switches in the two wire loop office release in the well known manner thereby opening the circuit of line relay 31 whichthereupon deenergizes. After an interval, slow to release relay 32 deenergizes and opens the locking circuits of relays 33 and 34 which thereupon deenergize. The operated switches in the battery pulse system releasein the well known manner thereby rendering said switches available for use. All of the apparatus in both systems are now in normal position. 1 1' It will now be assumed that a? calling sub scriber in the battery pulse office desires to complete a connection with a called .sub-

scriber located in the distant two wire loop oflice. It will further be assumed that responsive to the removal of the receiver bythe calling subscriber, the battery pulse switches are operated in the customary manner and that the selector S is operated and seizes an outgoing repeater for extending the connection to the two wire loop ofiice. It will fur-:

ther be assumed that selector S seizes the outgoing repeater OR shown in the drawings.

When this occurs a circuit for energizing the.

line relay 4; in the outgoing repeater OR may be traced as follows: from negative battery through the A lead of the selector S to the middle wiper of selector S,the A lead or conductor 25, and winding of relay l to ground. Relay 4:, upon energizing, at armature 13 closes a circuit for energizingslow to' release relay 5 and at armature ltprepares a point in a bridge clrcuit for across the conductors 1 and 2. Relay 5, upon energizing, at

armature 17 prepares a circuit for the slow ductor 27, winding of relay 3, conductor 55,

armature 54, and through the associated re-. sistance to battery. Relay 3 energizes over I the above traced circuit and at armature 11 opensanother point in the normal short circuit around itself and at its working contact prepares a point in the release circuit for the battery pulse switches. At armatures 10 and 12, relay 3 completes a bridge across the conductors 1 and 2 for energizing the line relay in the incoming switch in the two wire loop ofiice. The bridge extends from trunk conductor 1 by way of armature 10 and its working Contact, armature 15, armature 19 and its resting contact, upper winding of relay 7, normally closed springs controlled byarmature 23, lower winding of impedance 8, armature 14, working contact of armature 12 and said armature to conductor 2. The electropolarized relay 7 although included in the bridge, is not energized because the current flow through the upper winding is in the way of rela 9' over conductor26 OriFBTlead -i relay 7.

wrong direction. When the calling scriherdialsthe remaining digits in thetelephone number of thetcalledsubscriber, he

circuit ofline relay 4; is interrupted inthe Well known manner. Line relay 4: deenergizes responsive to the first-impulse and atnrmature 13 closes an energizing circuit for the slow to release series'relay 6. which thereupon energizes. At armatureg -l iline relay't opens the bridge across the trunk conduotors 1 and 2 thereby causing the line relay in the i eom in-g switch in the two wire loop .oflice to deenergize. :Series relay 6,;upon energizing, at armature 19 and its Working contact-closes a -directcurrlent' bridge across the conductors 1 an'cl2 in order to improve the impulsing circult. Relay (i however,v is maintained .enerrites relayodeenergizes opens the direct curnentbridge thereby again: substituting the bridge circuit 7 through the ,electroepolarized The, switches in the two wire loop office are operatedin the well known manner to extend the connection to the called subscr ber.

lVhenthe called subscriber answers, the con nector switch in the two wireloopofiice' reverses thedirection of current flow over the conductors 1 and 2,,tl ereby causing the. operation of the 'e'lectro nolarized {relay 7. Electric-polarized relayY, upon energizing at armature 20 shortcircuits the high resistanc 24'; and at armature :21 connects groundjbv to selector for controlling th'e switch super- ]vision or for causing the operation of the calling .subscribers meter as the case may be.

In case the called line was busy when called,;th'e connector inthe two Wire loop ofiice would not reverse T the direction of current 'flow. hut-instead would connect the busy tone to the trunk and the busy tone would'be transmitted to the calling subscriber-over the'heavy talking conductors in the'iwell known manner.

\Vhen conversation is terminated bothsub 7 scribersreplace-their receivers. The replacement ofthe receiver by the calling subscriber opens thecircuit of the line relaye, whe r,

upon said relay deenergizes, At armature 14 line relay 4 opens thebridge across the eon-r -00" switches inthe two wireloop office to release. in the well knownlmanner, Atari-mature 13 ductors 1 and 2 thereby permitting the relayt opens the circuit of the slow torelea-se relay '5 which, after an interval, re-

leases. At armature 18 relay ,5 opens the a l nemen circuit of relay 7 and at armature 16stopS the current flow through relay 3 by connect ing ground by Way of armature 11 to relay .3

toca-use sai-drelay-and the seleetorS to me lease, The deenergizing circuit for. relay 3 may be traced as follows: ground by Way of a working contact-0t armature 11 and said armature, armature lfi, relay 3, conductor 27 or lead, and through the test relayi-n the selector S to ground. Relay 3 in the outgol'ectorS deenergize, thereby causing the re.

to normal, The switches in the battery "pulse ofiiceare released and-returned to. their nor malpo'sition in the customary manner and may be used for extending further eon-nee tions.

ing repeater and the test relay in the se- 'peater OR and the selector Sto be returned. 1

Having described the invention, its utility andoperation, what is considered new and; is

desired tohaye protected by Letters-Patent will he set forth in the appended claims;

V I Wh at is'claimed is: 1 1

1." In a telephone system, afirst exchange, a

second exchange, a repeater in said second exchange, a two conductor tr-un-k'line connecting said exchangesand terminating in said repeater, a line'rjelay in said repeater hav? ing two windings connected to battery and ground, respectively; a' closed. incoming switch controlcircuitfincluding the two con ductors oi -said trunk line :and the t-W0 windings 0t said relay series,- an automatic switch in saidseoond exchange, a plurality 0st 7 conductors outgoing from said repeater and terminating in said switch, a second switch control circuit including' one pole of battery, only one of said outgoing oond'uctors a line relay infsaid s-witch',l' and the other pole oi battery,-means for interrupting said closed I (it) incoming switch control circuit-a plurality of 7 times to'cause the operation .ofsaid line relay in the repeater, andimeans controlled by'said line relay for interrupting said secondsw-itch control circuit a corresponding-number of times to operate the line relay in said switchthereby causing said switch. to extendaconnection.

only two conductors extending from the 7 exchange and terminatingin said repeater in the. secondlexchange, outgoing conductors extending from said repeateriand terminating in an automatic switch inthe seoondfiex change, means in said first -.exchange for-send ing loop impulses over the two conductorsof sald trunk llne in series to said repeater,

and means in said repeater res-ponsive' tore ceiving said loop impulses for retransmitting negative battery impulses out over only one of the outgoing conductors extending from said-repeater to said automaticiswitch to ex-tenda*connection.

3- 1 telelflhope ystem, two exchanges,

no r

" In a telephone systemytwo exchanges. an nnpulse repeater, .a trunk line comprising I an impulse repeater, a trunk line comprising only two conductors extending from the first exchange and terminating in said repeater in the second exchange, outgoing conductors extending from said repeater and terminating in an automatic switch in the second exchange, other automatic switches in the sec- 0nd exchange, means in said first exchange for sending loop impulses over the two conductors of said trunk line in series to said repeater, means in said repeater responsive to such loop impulses for re-transmitting a like number of negative battery impulses out over only one of the outgoing conductors of the repeater to cause said switch and said other switches to extend a connection to a called subscribers line, a source of busy signalling current in said repeater, means for automatically releasing said switch and said other switches in case the called line is busy, and means in said repeater responsive to said busy condition for automatically connecting said source to said trunk line.

4. In a telephone system, two exchanges, an impulse repeater, a trunk line comprising only two conductors extending from the first exchange and terminating in said repeater in the second exchange, outgoing conductors extending from said repeater and terminating in an automatic switch in the second exchange,

other automatic switches in the second exchange, means in said first exchange for sendmg loop impulses over the two conductors of said trunk line in series to said repeater, means in said repeater responsive to such loop impulses for retransmitting a like number of negative battery impulses out over only one of the outgoing conductors of the repeater to cause said switch and said other switches to extend a connection to a called subscribers line, means responsive to the called subscrib er answering for grounding another outgoing conductor of said repeater, and means in said repeater controlled over said second outgoing conductor independent of the first outgoing conductor for reversing the flow of current over the conductors of said trunk line. I

5. In a telephone system, two exchanges,

an impulse repeater in the second exchange,

a trunk line comprising only two conductors connecting said exchanges, said repeater nor-' mally disconnected from the conductors of said trunkline, incoming conductors terminating in said repeater, means for seizingv said repeater over said incoming conductors,

means in said repeater responsive to said seiz v ure for connecting said trunk conductors to said repeater and for closing abridge across the conductors of said trunk line, means for sponding number of loop impulses over the' ductors 01": said trunk line, and means in said 7 repeater responsive to said reversal for connecting ground to another of said incoming conductors for supervisory purposes.

6. In a telephone system, two exchanges, a trunk line comprising only two trunk conductors connecting said exchanges, two repeaters in the second exchange individual to said trunk line, outgoing conductors extending from the first of said repeaters, incoming conductors extending to the second of said repeaters, means in the first of said repeaters for receiving loop impulses over the two trunk conductors of said trunk linein series and for retransmitting negative battery impulses out over only one of said outgoing conductors of said first repeater, means in the second of said repeaters for receiving negative battery impulses over only one of said incoming conductors andfor i'etransmitting loop impulses over the two trunk conductors of said trunk line in series, means in the first of said repeaters responsive to ground being connected to the other of said outgoingconductors of saidfirst repeater for reversing the flow of current over the two trunk conductors of said trunk line for supervisory purposes,

and means in the se'condiof said repeaters responsive to a reversal of current over the two trunk conductors of said trunk line for connecting ground to the other of said incoming conductors of said second repeater for supervisory purposes. 5

7. In a telephone system, two exchanges, an impulse repeater, a two conductor trunk line extending from the first exchange and terminating in said repeater in the second exchange, a switch control circuit including both conductors-of said trunk in series, an automatic switch in the second exchange, outgoing conductors from said repeater ter minating in said automatic switch, a second switch control circuit including a source of battery in said repeater and only one of said outgoing conductors, and means in said repeater responsive to the closure of said first switch control circuit for closing said second switch control circuit. y

'8. In a telephone system, two exchanges, an impulse repeater, a two conductor trunk line extending irom the firstexchange and terminating in said repeater in the second exchange, a switch control circuit including both conductors of said trunk in series, an automatic switch in the second exchange,

outgoing conductors from said repeater terv minating in said automatic switch, a second switch control circuit including a source of battery in said repeater and only one of said for repeatingja like number of negative bat outgoing conductors, means in said repeater responsive to the closureof said first switch control circuit for closing said secondswitch' control circuit, and means responsive toint zerruptions of said first switch control cir- V" Cuitdor causing alikenumber of inter-' fifuptionsinsaid second switch control circuit I for extending a connection by operating said itch; e V

9,111 a'telephone'system, two exchanges s using diflerent switch control circuits, a two COhdllCtOI trunk line connecting said exchanges, a repeater in the second exchange individual to said trunk line but normally disconnected therefrom, automatic switches in said second exchange, a plurality of conductors incoming to said repeater and accessiswitch control circuits, two repeaters iii-the second exchange, means in one repeater for repeating impulses over said trunk 1ine,means in the other 'repeater'for' repeatingirnipulses received over said trunk line, means in each repeater for translatingfrom one system of switch control to another. I In witnesswl'iereof, I hereunto subscribe my namenthis 17th day of .FebrearmAgD.

, vroron s. T A-RR;

hhs te said automatic switches, means responsive to the seizureof said repeater over said incoming conductors for connecting Said repeater to said trunk llne and for closing a hridge'across the conductorsof said trunk line, and means in said repeater for receiving negative battery impulses over one of said incoming conductors and for producing alike ni'unber of interruptions in said bridge. i0. Ina telephone s stem, two exchangesus'ing different switch control circuits, a two conductor trunk line connecting said exdividual to said trunk line but normall'ydisconnected therefrom, automatic switches .in

changes, a repeater in the second exchange insaid second exchange, a plurality of conductors incoming to said repeater and accessible'to said automatic switches, means responsiv'e'to the seizure of said repeater over said incoming conductors for connectingsaid re peater to 'saidtrunk line and for closing a bridge across the conductors oit'said trunk line, means in said repeater for receiving negi ative-battery impulses over one of said in- 1 coming conductors and for producing like number of interruptions in said bridge, and" means responsive to the reversal of current flowj over said trunk line for connecting ground to another of said incoming con-j 'ductors for supervisory purposes.

v 11. In a telephone system, a two conductor mally connected to said tru'nk'line and the trunk line connecting two exchangestwo retpe at'ersln the "second exchange individual to said-trunk line, the*first repeater being nor second repeater beingnormall y' disconnected second repeater for: receiving imeccfinecting tw'e exchanges using difierent 

